[BAA Comets] CCD astrometry and photometry

[Roger Dymock]

Good afternoon all,

With help from Kevin Hills I have looked at the results we are getting from brighter comets such as
2P and C/2013 R1. It would appear that the procedure for obtaining visual equivalent magnitudes
breaks down for comets brighter than mag 10 or thereabouts. kphot cannot really handle those with
large comae which would seem to lead to the erroneous results. Uwe Pilz would like FoCAs to output
results for 'boxes' larger than 60x60" but this is not possible according to Julio Castellano as
such results would be error prone.

I therefore suggest that we put a limit of mag 10 on our procedure - comments welcome before I
update that procedure on the Project Alcock website.

I did notice, on COBS, that one imager has got good results for 2P/Encke using a DSLR camera and
processing the images with IRIS. Coincidentally I have recently been trying my hand at DSLR
astrometry and photometry so will pursue that avenue in parallel with writing 'Comets A to Z' (have
only got as far as D so it might take a while).

Finally if anyone obtains images of bright comets (RAW format and calibrated if possible) could they
please hang onto them as I may need a few examples to experiment with. Of course if any of you would
like to experiment yourselves please, please do.

Regards

Roger Dymock
Email: roger.dymock at ntlworld.com
Tel: 023 92647986
Skype: rogerdymock67 or
Skype: rjvdymock
MPC Observatory Code: 940
Project Alcock http://www.britastro.org/projectalcock/